Sink



FIG. 1 is a left-front perspective view of a sink showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right-side elevation view, the left side being a mirror image thereof;

FIG. 4 is a front elevation view thereof; and,

FIG. 5 is a back elevation view.

The broken line showing of plumbing openings is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a sink, as shown and described. 